202 GERM-CELL CYCLE IN ANIMALS 
gonia of the second order (Fig. 58, #). Those in- 
different germ cells that are to form odcytes grow 
large, remain in the germinal epithelium, and do not 
divide. They possess a double nucleolus (Fig. 58, F). 
When a diameter of 36 microns is attained, the 
odcyte passes out of the hermaphroditic gland into 
the uterus. 
The nurse cells, like the o6cytes, remain in the wall 
and do not divide; their nuclei grow to be about 15 
microns in diameter and the chromatin forms irregu- 
lar clumps more or less evenly distributed (Fig. 48, B). 
No differences could be discovered in the indifferent 
germ cells by means of which the future history of 
these cells could be determined. It was noted, how- 
ever, that egg cells were never present without a 
neighboring nurse cell, and the conclusion was 
reached that a favorable position with regard to a 
nurse cell determines whether an indifferent germ 
cell shall develop into a spermatogonium or an egg. 
If Buresch’s observations are correct, Helix is not 
protandric, but both sorts of germ cells mature at 
the same time, and the fate of an indifferent germ 
cell depends upon nutrition, that is, its proximity 
to a nurse cell. 
Demoll (1912b) has proposed a new hypothesis 
regarding sex determination and has selected certain 
events in the odgenesis and spermatogenesis of Helix 
pomatia as arguments in its favor. The hypothesis 
is that the accessory chromosome (see Chapter IX) 
contains the anlagen of the male sexual characters, 
whereas the female sexual characters are localized 
